RHP Processing in MRP Phase 2
Flow of RHP Packets on MRP Rings with Shared Interfaces shows an example of how RHP packets are processed normally in MRP rings with shared interfaces.
Port 1/2/1 on Ring 1 master node is the primary interface of the master node. The primary interface forwards an RHP packet on the ring. Since all the interfaces on Ring 1 are regular ports, the RHP packet is forwarded to all the interfaces until it reaches Port 1/2/2, the secondary interface of the master node. Port 1/2/2 then blocks the packet to complete the process.
On Ring 2, Port 1/3/1, is the primary interface of the master node. It sends an RHP packet on the ring. Since all ports on S4 are regular ports, the RHP packet is forwarded on those interfaces. When the packet reaches S2, the receiving interface is a tunnel port. The port compares the packet priority to its priority. Since the packet priority is the same as the tunnel port priority, the packet is forwarded up the link shared by Rings 1 and 2.
When the RHP packet reaches the interface on node S2 shared by Rings 1 and 2, the packet is forwarded since its priority is less than the interface priority. The packet continues to be forwarded to node S1 until it reaches the tunnel port on S1. That tunnel port determines that the RHP packet priority is equal to the port priority and forwards the packet. The RHP packet is forwarded to the remaining interfaces on Ring 2 until it reaches port 1/3/2, the secondary interface of the master node. Port 1/3/2 then blocks the packet to prevent a loop.
When the RHP packet from Ring 2 reached S2, it was also forwarded from S2 to S3 on Ring 1 since the port on S2 has a higher priority than the RHP packet. The packet is forwarded around Ring 1 until it reaches port 1/2/2, Ring 1 the secondary port. The RHP packet is then blocked by that port.